[PATCH] Introduce generic_file_splice_write_nolock()

This allows file systems to manage their own i_mutex locking while
still re-using the generic_file_splice_write() logic.

OCFS2 in particular wants this so that it can order cluster locks within
i_mutex.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 66 insertions, 14 deletions

diff --git a/fs/splice.c b/fs/splice.c
index c1072b6940c3..68e20e65c6e1 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -707,13 +707,12 @@ out_ret:
  * key here is the 'actor' worker passed in that actually moves the data
  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
  */
-ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
-                         loff_t *ppos, size_t len, unsigned int flags,
-                         splice_actor *actor)
+static ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
+                                  struct file *out, loff_t *ppos, size_t len,
+                                  unsigned int flags, splice_actor *actor)
 {
         int ret, do_wakeup, err;
         struct splice_desc sd;
-        struct inode *inode = out->f_mapping->host;
 
         ret = 0;
         do_wakeup = 0;
@@ -723,14 +722,6 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
         sd.file = out;
         sd.pos = *ppos;
 
-        /*
-         * The actor worker might be calling ->prepare_write and
-         * ->commit_write. Most of the time, these expect i_mutex to
-         * be held. Since this may result in an ABBA deadlock with
-         * pipe->inode, we have to order lock acquiry here.
-         */
-        inode_double_lock(inode, pipe->inode);
-
         for (;;) {
                 if (pipe->nrbufs) {
                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
@@ -803,8 +794,6 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
                 pipe_wait(pipe);
         }
 
-        inode_double_unlock(inode, pipe->inode);
-
         if (do_wakeup) {
                 smp_mb();
                 if (waitqueue_active(&pipe->wait))
@@ -815,6 +804,69 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
         return ret;
 }
 
+ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
+                         loff_t *ppos, size_t len, unsigned int flags,
+                         splice_actor *actor)
+{
+        ssize_t ret;
+        struct inode *inode = out->f_mapping->host;
+
+        /*
+         * The actor worker might be calling ->prepare_write and
+         * ->commit_write. Most of the time, these expect i_mutex to
+         * be held. Since this may result in an ABBA deadlock with
+         * pipe->inode, we have to order lock acquiry here.
+         */
+        inode_double_lock(inode, pipe->inode);
+        ret = __splice_from_pipe(pipe, out, ppos, len, flags, actor);
+        inode_double_unlock(inode, pipe->inode);
+
+        return ret;
+}
+
+/**
+ * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
+ * @pipe:       pipe info
+ * @out:        file to write to
+ * @len:        number of bytes to splice
+ * @flags:      splice modifier flags
+ *
+ * Will either move or copy pages (determined by @flags options) from
+ * the given pipe inode to the given file. The caller is responsible
+ * for acquiring i_mutex on both inodes.
+ *
+ */
+ssize_t
+generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
+                                 loff_t *ppos, size_t len, unsigned int flags)
+{
+        struct address_space *mapping = out->f_mapping;
+        struct inode *inode = mapping->host;
+        ssize_t ret;
+        int err;
+
+        ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
+        if (ret > 0) {
+                *ppos += ret;
+
+                /*
+                 * If file or inode is SYNC and we actually wrote some data,
+                 * sync it.
+                 */
+                if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
+                        err = generic_osync_inode(inode, mapping,
+                                                  OSYNC_METADATA|OSYNC_DATA);
+
+                        if (err)
+                                ret = err;
+                }
+        }
+
+        return ret;
+}
+
+EXPORT_SYMBOL(generic_file_splice_write_nolock);
+
 /**
  * generic_file_splice_write - splice data from a pipe to a file
  * @pipe:       pipe info